CLASSIFICATION 7 



applied to it. But in culture media, the organism resembles a true 

 coccus, being globular and growing in chains. It is then called 

 the Streptococcus lanceolatus. It is common also to speak of 

 members of the family of Mycobacteriacece as bacilli, as they are 

 more commonly met with in this form in clinical examinations, and 

 in cultures. Hence, we frequently hear of the bacillus of tubercu- 

 losis, and not the Mycobacterium tuberculosis. 



Among the higher bacteria, the differentiation of those belonging 

 to the sheathed group, or Chlamydobacteriacece, is difficult, as it 

 depends largely upon the formation of the false branching and the 

 gonidia. When bacteria exhibit many, or various forms, in the 

 same culture, as does the typhoid bacillus, we speak of it as pleo- 



FIG. 4. Cholera vibrios. FIG. 5. Spirillum relapsing fever. 



(Greene's Medical Diagnosis.) (Greene's Medical Diagnosis.) 



morphic, or pleomorphism. To elucidate: Man is pleomorphic, 

 because among adult individuals some are tall or short, fat or thin. 

 ^ Involution or Degeneration forms. When the best or optimum 

 conditions for bacterial life (see page 17) are not found, bacteria 

 present appearances quite different from those of the young, active 

 or perfect adult type. These are called involution or degeneration 

 forms. For example: the diphtheria bacillus under good conditions 

 for life is a straight or slightly bent rod staining in a granular man- 

 ner. If living under unsuitable conditions it becomes quite short, 

 and stains solidly. Again bacilli that are~ accustomed to appear as 

 short elements may grow to long threads without dividing, or swell 

 into unrecognizable form. / 



